We propose to develop novel anobioconjugates for the treatment of breast cancer by inhibiting angiogenesis and stimulating the host immune system simultaneously. The nanobioconjugates are based on a biodegradable and non-toxic polymalic acid nanoplatform with covalently attached anti-transferrin receptor (TfR) monoclonal antibody for delivery through the endothelial system of the tumor vasculature, antisense oligonucleotides (AON) to inhibit angiogenesis, and/or potent immunostimulatory antibody-cytokine fusion proteins specific for the breast cancer antigen HER2/neu. We hypothesize that the new nanobiopolymers when used alone or in combination would be capable of a multi-pronged attack against cancer cells by inhibiting tumor angiogenesis with the subsequent induction of apoptosis and by activating innate and adaptive immune responses resulting in long-term anti-tumor immunity not only against HER2/neu but also against other tumor antigens. In addition, the nanobioconjugates would exhibit superior tumor targeting as a consequence of the combination of transcytosis mediated by TfR overexpressed on the endothelial cells of the tumor neovasculature, targeting of HER2/neu or TfR overexpressed by the tumor, and the enhanced permeability and retention (EPR) effect exhibited by nanopolymers. The anti-angiogenic effect would be achieved using AON to inhibit the expression of vascular protein laminin-411 and/or vascular endothelial growth factor (VEGF), critical factors produced by the cancer cells needed to develop new vasculature that supports the tumor. In addition, to achieve HER2/neu targeting and immunoactivation we will use the potent immunostimulatory cytokines interleukin-2 (IL-2) or interleukin-12 (IL-12) that would be delivered into the tumor by an anti-HER2/neu IgG3-cytokine fusion protein as part of the nanobiopolymer. We will also explore the effect of combining free antibody-cytokine fusion proteins with the anti-angiogenic nanopolymer. Importantly, IL-12 is also an anti-angiogenic cytokine increasing the anti-angiogenic effect of AON. The proposed nanobiopolymers represent novel and unique molecules in terms of structure and mechanisms of action. To the best of our knowledge, neither the proposed therapeutic nor other molecules with similar mechanisms of action have either been described or are under development. The specific aims of this project are: Aim 1. Synthesis and in vitro characterization of nanobiopolymers, Aim 2. Initial pharmacokinetic and toxicological studies of the nanobiopolymers, and Aim 3. Examine the ability of nanobiopolymers to inhibit tumor growth and investigate the mechanism responsible for anti-tumor protection and immunological memory. The proposed nanobiopolymers represent the starting point for a new generation of cancer therapeutics and are expected to be effective against aggressive breast cancer tumors such as those overexpressing HER2/neu. A novel nanobiopolymer-based therapy against HER2/neu expressing cancer cells with sufficient capacity to inhibit angiogenesis and orchestrate an anti-tumor immune response should make a significant clinical impact.